Derivative Instruments and Hedging Activities - Schedule of Estimated Gross Fair Values of Derivative Instruments and Their Classification on Consolidated Balance Sheet (Details) - Cash Flow Hedges - Derivatives Designated as Hedging Instruments - Interest Rate Swap Agreements $ in Thousands	Sep. 30, 2019 USD ($)
Liabilities:
Derivative liabilities	$ 21,419
Current Portion of Long-term Liabilities
Liabilities:
Current portion of long-term liabilities	4,675
Other Long-term Liabilities
Liabilities:
Other long-term liabilities	$ 16,744